Re: help with Wrong type of argument

[Jean Abou Samra]

Le lundi 01 mai 2023 à 12:52 +0200, Lukas-Fabian Moser a écrit :

There's one other way which is sometimes useful (but admittedly won't simplify the present use case much):

#`((lineto 0 ,hgt) (closepath))

is the a list with two elements, namely

• the 3-element list containing 'lineto, 0 and the value of the variable hgt
• the 1-element list containing the symbol 'closepath.

This may also be written as:

#(list (list 'lineto 0 hgt) (list 'closepath))

or, mixing the two styles,

#(list (list 'lineto 0 hgt) '(closepath))

Well, these styles are almost equivalent but not quite; the difference trips up people at times.

I think I need to briefly mention this fact somewhere in the tutorial; most of the times it doesn't matter, but in the few cases where it does, tracking down the problem can be extremely confusing if you are not aware of this subtlety.

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